Grid electrodes for electron discharge devices



April 19, 1960 c. F. MILLER ETAL GRID ELECTRODES FOR ELECTRON DISCHARGE DEVICES Filed Feb. 10, 1956 4| 5 F m. I s m m 2 2 E W m 7. I ,n H-LM: t Y 2 Carl F. Miller,Clifford E. Homer, Williom H. Mew? Donald R. Quinn.

WITNESSES A W@ WW GRID ELECTRODES FOR ELECTRON DISCHARGE DEVICES Carl F. Miller, Bath, Clifford E. Hornet, Watkins Glen,

and Wiliiam H. McCurdy and Donald R. Quinn, Horseheads, N.Y., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 10, 1956, Serial No. 564,741

6 Claims. (Cl. 204-11) This invention relates to electron discharge devices and, more particularly, to grid electrodes suitable for use in ultra-high frequency electron discharge devices.

Prior art grid electrodes of the type in which grid lateral Wires are supported by side rod members are not satisfactory for many uses because of their case of distortion. A sturdier grid electrode may be made by winding grid lateral wires over a grid electrode frame member but complicated winding and brazing operations are involved. Etched grids and electrodeposited grid meshes for ultra-high frequency electron discharge devices are extremely fragile because of their thinness. This fragility leads to considerable difiiculties involved in attaching these grids and meshes to suitable frames. In general, our invention relates to a sturdy grid electrode in which the grid wires or meshes are plated on a rigid grid frame at the sametime as at least part of the grid frame itself is placed so that the grid wires or meshes become an integral part of the grid frame, thus reducing distortion and uneven tension.

It is an object of this invention to provide a process for electroplating a grid or a mesh on a rigid grid frame member.

It is a further object to provide an improved process for making a grid electrode in which process the grid wires are made an integral part of the grid frame member.

An additional object is to provide an improved grid electrode of sturdy constructionin which distortion is low.

It is another object to provide an improved process for making a grid electrode, which process is suitable for automatic production procedures.

It is still another object to provide an improved grid electrode which operates at lower temperatures than comparable grid electrodes and therefore has less primary emission thancomparable grid electrodes.

These and other objects of the invention will be apparent from the following description taken in accordance with the accompanying drawing which forms a part of this application, and in which:

Figure l is a front view of a grid electrode frame member;

Fig. 2 is a side sectional view of the grid electrode frame member of Fig. 1 into the aperture of which an insert member has been placed;

Fig. 3 is a front view of a grid electrode frame member after portions of the resist material have been removed;

- Fig. 4 is a side sectional view of the grid electrode frame member shown in Fig. 3; i

' Fig. 5 is a front view of a grid electrode made according to one embodiment of applicants invention;

Fig. 6 is a side sectional view of the grid electrode shown in Fig. 5;

Fig. 7 is a side sectional view showing the step of exposure of the photo-resist material;

Fig. 8 is a side sectional view of a grid electrode frame member with a recessed insert member; and

Fig. 9 is a side sectional view of a grid electrode made according to another embodiment of our invention,

Referring to Figs. l-6, a grid electrode and a method for making it are described in accordance with our invention. In Fig. 1 there is shown a front View of a grid electrode frame member 11 having an aperture 13. The grid electrode frame member 11 may be made of a material such as iron, nickel or other similar metals.

In Fig. 2 there is shown a grid electrode frame member 11 similar to that shown in Fig. 1, in the aperture 13 of which an insert member 15 has been positioned. This insert member may be made of a malleable metal such as copper and, after it is positioned, the front. surface 19 of the insert member 15 is made flush with the front surface 17 of the grid electrode frame member 11. This may be done by methods such as grinding, polishing, etc. Special care must be taken to obtain intimate contact between insert member 15 and the sides of the aperture 13 in order to avoid discontinuities in the subsequent plating.

After the front surface 17 of the grid electrode frame member 11 and the front surface 19 of the insert member 15 are made flush with each other, they are covered with a non-conducting material which will prevent electrodeposition. Such a material is called a resist. A 5% solution of polybutyl methacrylate in toluene: is suitable for this purpose. This non-conductive resist material, after drying, is scratched with a suitable instrument to produce parallel grooves such as shown in Fig. 3. As seen in Fig. 3, resist material 21, after scratching, consists of resist free areas 25 and remaining portions 23 of the resist material 21.

In Fig. 4 there is shown a side sectional view of Fig. 3 showing the grid electrode frame member 11, insert member 15, resist material 21, resist free areas 25 and the remaining portions 23 of the resist material 21.

After portions of the resist material have been re moved, as shown in Figs. 3 and 4, the grid electrode frame member 11 may now be electroplated on the exposed conductive areas with any metal which is suitable for an electronic grid structure. For example, nickel has been shown to be such a suitable metal. Nickel may be electroplated from an elecrtoplating bath consisting of 240 grams of nickel sulphate, 45 grams of nickel chloride and 30 grams of boric acid per liter of solution. This plating bath is heated to approximately F. and the plating is done at a cathode current density of 0.4 ampere per square inch. After the plating process is completed, the resist material may be removed by dissolving in toluene and the insert member 15 is then removed. This latter removal may be accomplished by placing the grid electrode frame member 11 into a 10% sodium cyanide solution which will dissolve the edges and reduce the dimensions of the copper insert member 15, thus allowing this insert member 15 to be easily displaced. If desired, this removal of the insert member 15 can be hastened by making the assembly anodic in an electrolytic plating bath.

Fig. 5 shows a grid electrode which may be made by the above method including a grid electrode frame member 11, an aperture 13 and grid lateral wires 27. It should be noted that the grid lateral wires 27 extend across the aperture 13 and also across the grid electrode frame member 11. Thus, the grid lateral wires 27 have become an integral part of the grid electrode frame member 11. If desired, closer bonding may be obtained by annealing the structure which will cause diffusion of the electroplated material and the base material of the grid electrode frame member 11. Also, if desired, the grid electrode frame member 11 may be completely covered with electroplated material rather than the partial covering as shown in Fig. 5.

In Fig. 6 there is shown a side sectional view of the complete grid electrode shown in Fig. including the grid electrode frame member 11, the aperture 13 and the grid lateral wires 27.

Another method of preparing the grid electrode is by the use of a photo-resist material which is sensitive to actinic radiation. One such photo-resist material is sensitized polyvinyl alcohol. After the front surface 17 of the grid electrode frame member 11 and the front surface 1% of insert member have been coated with such a photo-resist material 21, the photo-resist material 21 is exposed to actinic radiation 33 through a pattern member 29. As shown in Fig. 7, some portions of the resist material 21' are exposed to the actinic radiation 33, while other portions 31 remain in the shadows. As actinic radiation, such as ultra-violet light in this particular case, makes photo-resist material 21' insoluble, the

unexposed portions, namely, the shadow areas 31 of the photo-resist material 21, may be easily removed by washing with water. Then the specimen may be plated and the insert member removed as described above. Any

The above photo-resist method may be used to make an electroplated grid electrode with a carbon layer on one side as described below. This carbon layer, which is particularly effective if located on the surface of the grid opposite the cathode, will suppress emission from the grid surface itself. Also, as the carbon layer increases the thermal radiation properties of the grid electrode, the temperature of the grid will be lowered thereby aiding in reducing emission from the grid surface.

A base material which may be composed of a ceramic or of a metal such as nickel is smoothed on one side. This base material must be of a material which is able to withstand the subsequent firing at a temperature of from 400 to 500 C. The smooth side of this base material is coated with a film of a fine graphite powder suspended in a solution of polybutyl methacrylate in toluene. We have found a 25 grams suspension of a fine air-spun graphite in 100 cc. of the toluene-polybutyl methacrylate solution to be satisfactory. Other vehicles of suspension may be used rather than polybutyl methacrylate and the suspension may be applied to the base member by spraying, painting or dipping. After this film is dried, it is coated with a photo-sensitive material and, after drying, is subsequently exposed to actinic radiation through a template having apertures as desired for the final gr id electrode. As discussed previously, the exposed portions of the photosensitive material become insoluble in water. The unexposed portions of the photosensitive material are then removed by washing in water and the specimen is plated with a metal such as nickel to the desired thickness. fired for approximately 60 minutes at a temperature of 400 C. in a reducing atmosphere to decompose the remaining photosensitive layer and also to decomposethe suspending material of the carbon film. The carbon layer then'sinters into the plating. The grid may be stripped from the base material if desired and any loose carbon particles clinging to the grid apertures may be easily removed by mechanical means such as light brushing.

This method of applying a carbon coating may also be used in an aperture mask of a color television cathode ray tube. I

In Fig. 8 there is shown a grid electrode frame member 11 and an insert member 35 which has been posi- Photo-resist materials,

Next, the specimen is tioned in the aperture 13 of the grid electrode frame member 11 in such a manner as to provide a recessed portion 37 into which resist material 39 has been placed. Resist material 39 is also placed on the front surface 17 of the grid electrode frame member 11. After the removal of portions of the resist material 3% as described above, grid lateral wires 41 are placed into the portion 37. After the insert member 35 and any remaining resist material 47 has been removed, we will obtain grid lateral wires 4-1 located within the aperture 13 of the grid electrode frame member 11 as shown in Fig. 9. The recessed portion 37 may be obtained by making the insert member 35 of slightly less thickness than the grid electrode frame member 11 and make the back surface 43 of the insert member 35 flush with the back surface 45 of the grid electrode frame member 11.

A grid electrode constructed in the manner shown in Figs. 8 and 9 has certain advantages in that more accurateinterelectrode spacing may be obtained as the front surface 17 of the grid electrode may be made to be in the same plane as the front surface 18 of the grid lateral wires 41.

If desired, the insert member 15 or 35 may be made of a low temperature solder material which can be removed from the grid electrode frame member 11 by a heating method such as immersion. inboiling water. The above disclosed grid electrode lends itself to a continuous automatic process through the following steps: (l) A continuous strip of grid electrode frame members are pierced or formed.

(2) Insert 'members are positioned, as desired, within the grid electrode frame members.

(3) The grid electrode frame members and'insert members are cleaned.

(4) Photo-resist material is applied.

(5) Fhoto-resist material is dried.

(6) Photo-resist material is exposed to actinic radia. tion.

(7) The unexposed portions of the photo-resist material are removed.

(8) A grid electrode pattern is plated upon the grid electrode frame members.

(9) The completed strip is washed.

(10) The insert member is removed.

(11) The finished strip is washed.

'(12') Any remaining photo-resist'material is removed.

('13) The finished grids are detached from each other as described.

It is, of course, understood that rather than having the grid lateral wires in the form of electro-plated strips they may be in the form of meshes or other desired designs.

While the present invention has been shown in a few forms only, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various.

changes and modifications without departing from the spirit and scope thereof.

We claim as our invention:

l. A method of making grid electrodes suitable for use in electron discharge devices, said method including the steps of forming a grid electrode frame member, said grid electrode frame member having an aperture and a planar front surface, said aperture being sourrounded by said frame member, positioning a solid insert member within said aperture so that one surface of said in sert member is flush with said front surface, placing a resist material upon said insert member and upon said front surface, removing portions of said resist material so. that desired areas are free of resist material, electroplating metal material in said resist-free areas, and removing said insert member from said aperture so that portions of said metal material extend across certain desired portions of said aperture.

2. A method of making grid electrodes suitable for use in electron discharge devices, said method including the steps of forming a grid electrode frame member, said grid electrode frame member having a planar surface and an aperture therein, positioning a solid insert member having a planar surface within said aperture so that said planar surface of said insert member is flush with said planar surface of said grid electrode frame member, placing a resist material upon said flush planar surfaces, removing portions of said resist material so that desired areas are free of resist material, electroplating metal material in said resist-free areas, and removing said insert member from said aperture so that first portions of said metal material cover portions of said surface of said grid electrode frame member, so that second portions of said metal material extend across certain desired portions of said aperture thereby forming grid laterals integral with said grid electrode frame member and so that said first and second portions lie in the same plane.

3. A method of making grid electrodes suitable for use in electron discharge devices, said method including the steps of forming a grid electrode frame member, said grid electrode frame member having a planar surface and an aperture therein, positioning a solid insert member having a planar surface Within said aperture, making said planar surface of said insert member flush with said planar surface of said grid electrode frame member, placing a photosensitive resist material upon said. flush planar surfaces, masking said resist material with a desired pattern, exposing portions of said resist material to actinic radiation through said pattern, removing the unexposed portions of said resist material thereby forming resist-free areas, electroplating metal upon said resist-free areas, and removing said insert member from said aperture so that first portions of-said metal material cover portions of said surface of said grid electrode frame member, so that second portions of said metal material extend across certain desired portions of said aperture thereby forming grid laterals with said grid electrode frame member and so that said first and second portions lie in the same plane.

4. A method of making grid electrodes suitable for use in electron discharge devices, said method including the steps of forming a grid electrode frame member, said grid electrode frame member having a planar surface and an aperture therein and being attached to other grid electrode frame members, positioning a solid insert member within said aperture, said insert member having a planar surface making said planar surface of said insert member flush with said planar surface of said grid electrode frame member, placing a photosensitive resist material upon said flush planar surfaces, masking said resist material with a desired pattern, exposing portions of said resist material to actinic radiation through said pattern, removing the unexposed portions of said resist material thereby forming resist-free areas, electroplating metal on said resist-free areas, removing said insert member from said aperture so that first portions of said metal material cover portions of said surface of said grid electrode frame member, so that second portions of said metal material extend across certain desired portions of said aperture thereby forming grid laterals integral with said grid electrode frame member and so that said first and second portions lie in the same plane, and detaching the grid electrode frame member from the other grid electrode frame members,

5. A grid electrode member suitable for use in electron discharge devices, said grid electrode member including a metallic grid electrode frame member, said grid electrode frame member having an aperture and a planar front surface, said electrode frame member completely surrounding said aperture, a first portion of electrodeposite-d metallic material at least partially covering said front surface and being united therewith, and a second portion of electrodeposited metallic material partially covering and extending across desired portions only of said aperture, said second portion being integral with said first portion and lying in the same plane as said first portion.

6. A grid electrode member suitable for use in electron discharge devices, said grid electrode member including a metallic grid electrode frame member, said grid electrode frame member having an aperture and a planar front surface, said electrode frame member completely surrounding said aperture, a first portion of electrodeposited metallic material completely covering said front surface and being united therewith, and a second portion of electrodeposited metallic material partially covering and extending across desired portions only of said aperture, said second portion being integral with said first portion and lying in the same plane as said first portion.

References Cited in the file of this patent UNITED STATES PATENTS 1,820,240 Michell Aug. 25, 1931 2,287,122 Norris June 23, 1942 2,533,533 Stoddard Dec. 12, 1950 2,641,439 Williams June 9, 1953 2,692,190 Pritikin Oct. 19, 1954 2,699,424 Nieter Jan. 11, 1955 2,761,828 Eldredge et a1. Sept. 4, 1956 2,795,032 Kernstetter June 11, 1957 

1. A METHOD OF MAKING GIRD ELECTRODES SUITABLE FOR USE IN ELECTRON DISCHARGE DEVICES, SAID METHOD INCLUDING THE STEPS OF FORMING A GRID ELECTRODE FRAME MEMBER, SAID GRID ELECTRODE FRAME MEMBER HAVING AN APERTURE AND A PLANAR FRONT SURFACE, SAID APERTURE BEING SOURROUNDED BY SAID FRAME MEMBER, POSITIONING A SOLID INSERT MEMBER WITHIN SAID APERTURE SO THAT ONE SURFACE OF SAID INSERT MEMBER IS FLUSH WITH SAID FRONT SURFACE, PLACING A RESIST MATERIAL UPON SAID INSERT MEMBER AND UPON SAID FRONT SURFACE, REMOVING PORTIONS OF SAID RESIST MATERIAL SO THAT DESIRED AREAS ARE FREE OF RESIST MATERIAL, ELECTROPLATING METAL MATERIAL IN SAID RESIST-FREE AREAS, AND REMOVING SAID INSERT MEMBER FROM SAID APERTURE SO THAT PORTIONS OF SAID METAL MATERIAL EXTEND ACROSS CERTAIN DESIRED PORTIONS OF SAID APERTURE. 